Apparatus for continuously drying web material especially textile material

ABSTRACT

APPARATUS FOR CONTINUOUSLY DRYING WEB MATERIAL, ESPECIALLY TEXTILE MATERIAL, IN WHICH THE MATERIAL IS FED ONTO AN ELONGATED AIR-PERMEABLE CONVEYOR MOVING IN LONGITUDINAL DIRECTION AND IN WHICH AT LEAST AT ONE LONGITUDINAL PORTION OF THE CONVEYOR AIR IS PASSED IN DOWNWARD DIRECTION THROUGH THE CONVEYOR AND THE WEB SUPERIMPOSED THEREON SO THAT THE WEB WILL ADHERE TO THE CONVEYOR BE TRANSPORTED THEREBY IN LONGITUDINAL DIRECTION, IN WHICH AT LEAST IN ANOTHER LONGITUDINAL PORTION OF THE CONVEYOR   ADJACENT TO THE ONE PORTION AIR IS PASSED IN UPWARD DIRECTION THROUGH THE CONVEYOR AND THE SUPERIMPOSED WEB THAT THE LATTER IS LIFTED FROM THE CONVEYOR, AND IN WHICH MEANS ARE PROVIDED ABOVE THE OTHER PORTION OF THE CONVEYOR FOR LIMITING MOVEMENT OF THE WEB AWAY FROM THE CONVEYOR.

1971 RTTSOLDENBERG ErAL APPARATUS FOR CONTINUOUSLY DRYING WEB MATERIAL, ESPECIALLY TEXTILE MATERIAL Fued Oct. 24, 1969 5 Sheets-Sheet 1 IN VEN TOR MM"... aw, uMW WM 6 WmS hw 6 L PM D M R54 1971 R. GOLDENBERG ETAL 3,618,226

APPARATUS FOR CONTINUCUSLY DRYING WEB MATERIAL, ESPECIALLY TEXTILE MATERIAL Filed Oct. 24, 1969 5 Sheets-Sheet 2 IN VEN TOR Roar COMEIV 8546 5y El/Cl/ Mme/M T 46PM)! MM IL? Nov. 9, 1971 R. GOLDENBERG ETAL 3,618,226

APPARATUS FOR CONTINUOUSLY DRYING WEB MATERIAL, ESPECIALLY TEXTILE MATERIAL Filed Oct. 24, L969 5 Sheets-Sheet J IN VEN TOR 004 r 60605411361 cr BY Mm 11/06 0T 44mm 5cm INF mmlw/ (A-4r Nov. 9, 1971 GOLDENBERG ETAL 3,618,226

APPARATUS FOR commuousm' DRYING WEB MATERIAL, ESPECIALLY TEXTILE MATERIAL Flled Oct 24, 1969 5 Sheets-Sheet 4 Kym W mmwm NAM. A, wwwm m NMM f 0 4 aw d mm 4 l. 1 we Q m mm B cm mm m 5 Sheets-Sheet 5 IlllllllII-III ESPECIALLY TEXTILE MATERIAL R. GOLDENBERG ET AL APPARATUS FOR CONTINUCUSLY DRYING WEB MATERIAL,

Nov. 9, 1971 Filed Oct. 24,

INVENTOR Roar 6004506016 ldbrdul United States Patent Office 3,618,226 Patented Nov. 9, 1971 3,618,226 APPARATUS FOR CONTINUOUSLY DRYING WEB MATERIAL, ESPECIALLY TEXTILE MATERIAL Rolf Goldenberg, Erich Hilgeroth, and Alfons Schrader,

Remscheid-Lennep, Germany, assignors to Maschinenfabrik Friedrich Haas & (30., Remscheid-Lennep, Germany Filed Oct. 24, 1969, Ser. No. 869,163 Int. Cl. F26b 13/12 U.S. Cl. 34-156 17 Claims ABSTRACT OF THE DISCLOSURE Apparatus for continuously drying web material, espe cially textile material, in which the material is fed onto an elongated air-permeable conveyor moving in longitudinal direction and in which at least at one longitudinal portion of the conveyor air is passed in downward direction through the conveyor and the web superimposed thereon so that the web will adhere to the conveyor to be transported thereby in longitudinal direction, in which at least in another longitudinal portion of the conveyor adjacent to the one portion air is passed in upward direction through the conveyor and the superimposed web so that the latter is lifted from the conveyor, and in which means are provided above the other portion of the conveyor for limiting movement of the web away from the conveyor.

BACKGROUND OF THE INVENTION The present invention relates to drying apparatus for webs and especially webs of textile material. The dryer of the present invention is adapted to dry continuous or discontinuous webs of material, for example tricot underwear.

When drying webs of textile materials, such as tricot material, considerable difliculties arise. As known, attention has to be directed not only to the quality and color fastness of the material, but shrinkage poses a special problem, especially in knitted goods made from cellulosic yarns or blends of different yarns, for example knitted fabric for lingerie, garments and the like. It is known that the causes of shrinkage are to be attributed to tensions which arise during the preparation, mainly in spinning and knitting yarns or during finishing the fabric itself, and a complete compensation for such tensions by means of shrinkage has so far not been obtained. Residual tensions which are not compensated during the course of production of a garment then cause shrinkage to a greater or lesser degree after the first washing. A fully shrunk knitted fabric is, on the contrary, free of tension.

It is possible to differentiate between the various types of stretching. First of all, there is a resilient stretching. This part of the stretching may be disregarded, because the stretched knitted fabric immediately returns to the original dimensions upon relaxation. A further stretch is represented by the viscous-resilient part, for whose compensation the knitted fabric requires a certain time in order to return to the original dimensions after relaxation. Finally, a plastic stretch part has to be considered, which after relaxation remains as a residual stretch. In this connection, it should also be taken into account that the resilient stretch is considerably greater in a dry fabric than in a wet fabric. This can be attributed, for example, in wet cotton threads, to the increased swelling of the threads.

Starting from the considerations briefly set out above, the invention is based on the recognition that during the drying a shrinkage of the fabric takes place, due to the decline of the swelling of the fibers. In a regulated fabric having a straight formation of the meshes, the tension can consequently be compensated to a considerable degree by drying, provided that such drying occurs free from tension.

Dryers are already known wherein a web of material is passed therethrough free of tension, so that a natural shrinkage can take place. Such dryers have proved very satisfactory in practice, but they require a relatively large amount of space and construction costs are high in rela tion to the efliciency of the drying produced.

The invention is based on the further recognition that the drying process can be split up into a plurality of sections, namely:

(1) A heating-up section in which surface evaporation will start;

(2) A second section in which an even drying with slightly decreasing drying speed will take place;

(3) A third section in which evaporation of the swelling water with a much decreasing speed of drying will be obtained; and

(4) A fourth section in which evaporation of the residual capillary water in the interior of the fibers in dependence on the conditions of diffusion of the material will take place with a much reduced drying speed up to the hygroscopic balance with the drying air.

The drying is conveniently discontinued after the fourth section to assure that overdrying, i.e., evaporation of the natural hygroscopic liquid content does not take place. Considering a four-stage drying process, as set forth above, it is possible to differentiate basically between two drying sections, namely, on the one hand, the heating up and evaporation of the surface moisture and, on the other hand, the relaxation and thereby the shrinkage of the material by evaporation of the swelling and capillary water in the threads of fibers.

On the basis of these latter considerations, the conclusion has been drawn in arriving at the present invention, that in the first drying section, evaporation of the surface moisture should take place without any great effect on the shrinkage so that in this drying stage conditions of drying can :be selected using relatively high air speeds. In the second drying section, in contrast to the first, the material must be able to shrink freely both longitudinally and transversely. Here the air speeds must be lower, not only in order to decrease the dynamic forces of the air, but also to obtain an even shrinkage over the crosssection of the yarns and fibers and to thereby improve the quality of the fabric.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a dryer which assures high specific efficiency of water evaporation and a good shrinkage effect.

It is a further object of the present invention to provide a dryer of the aforementioned kind which requires a relatively small space and which can be economically produced.

With these and other objects in view, the apparatus according to the present invention for the continuous drying of Web material mainly comprises a substantially horizontally arranged elongated, air-permeable conveyor means for transporting a web to be dried in longitudinal direction, means for sucking air in at least one longitudinal portion of the conveyor means in one direction through the latter so that the web superimposed thereon will be held in engagement with the conveyor means and for blowing air in at least another longitudinal portion of the conveyor means, adjacent to the one portion, in a direction opposite to the one direction through the same so as to lift the web from the other portion of the conveyor means, and means arranged at least along the other portion of the conveyor means and spaced in said opposite direction therefrom for limiting movement of the web away therefrom.

The drying apparatus preferably includes an elongated housing forming a drying chamber, and heating means for heating the air which is passed through the conveyor means and the web are located in the drying chamber.

The means for limiting movement of the web away from the other portion of the conveyor means may comprise a plurality of rollers extending spaced from each other in direction of movement of said conveyor means and transverse to this direction above the other portion of the conveyor means. The rollers may be rotated in stationary hearings in dependence on the speed of the conveyor means and the shrinkage arising in the web. On the other hand, the rollers may be hollow and stationarily mounted and be provided over an are facing the Web with holes for the passage of compressed air therethrough which is fed into the interior of the hollow rollers.

In another form of the apparatus according to the present invention, the means for limiting movement of the web away from the first-mentioned conveyor means may be constituted by a second similar conveyor means which has a run extending substantially parallel and upwardly spaced from the first conveyor means so that in the one longitudinal portion of the first conveyor means the web of material will rest on the first conveyor means and in each second portion will rest against the second conveyor means. Preferably, the distance between the two conveyor means amounts toa multiple of the thickness of the web of material to be dried.

The first and the second conveyor means may be driven with the same or with dilferent speeds and such speeds may also diifer from the speed at-which the web of material is fed onto the conveyor means.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal cross-section through a dryer according to the present invention;

FIG. 2 is a cross-section taken along line IIII of FIG. 1; 2

FIG. 3 is a cross-section taken along the line IIIIII of FIG. 1;

FIG. 4 schematically illustrates a detail of part of the apparatus of FIG. 1 on an enlarged scale;

FIG. 5 is a cross-section on an enlarged scale through a hollow roller which may be used in the apparatus;

FIG. 6 is a cross-section on an enlarged scale through a driven roller which may be used in the apparatus;

FIG. 7 is a longitudinal section of a modified form of dryer according to the present invention;

FIG. 8 is a detail of part of the dryer of FIG. 7 drawn to an enlarged scale; and

FIGS. 912 are schematic views illustrating the manner in which the web will pass through the space between the two conveyor means of a drying apparatus similar to that shown in FIG. 7, depending on the speed of the two conveyor means and the speed with which the web is fed into the space between the two conveyor means.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawing, and more specifically to FIGS. 1-4 of the same, it will be seen that the dryer according to the present invention may include a drying chamber enclosed by an elongated housing 1, into which webs 2 of textile material, preferably one or more webs of knitted goods extending adjacent to each other, are to be introduced through an inlet opening in the housing. The dryer may include an entrance chamber In, arranged at the left side, as viewed in FIG. 1, of the housing 1, and this entrance chamber is provided with a pair of guide rollers 3 and 4 and a delivery roller 5. At the opposite end of the dryer is provided a take-off roller 6-. The Webs 2 pass, as will be explained in greater detail below, through individual sections of the apparatus on an air-permeable endless conveyor belt 7 and the latter is carried by guide rollers 8, 9, 10 and 11. The roller 9 is driven, for example by a chain drive 13 from a motor 12. Evidently different means for driving the conveyor belt 7 may be used. On its lower run the conveyor belt may be supported by additional rollers 34 and 35 or other forms of support. The roller 11 is preferably adjustable ina known manner for the purpose of tensioning the conveyor belt.

Axial flow fans 14 and 15 having their drive shafts at right angles to the conveyor are located spaced from each other in direction of movement of the conveyor belt below the upper run of the latter. Pulleys 17 fixed to the lower ends of the drive shafts are driven by means of drive belts 18 from motors 19, as best shown in FIG. 2.

As can be seen from FIG. 1, the drying chamber formed by the elongated housing 1 is divided into four sections, i.e., the sections 20, 21, 22 and 23. The air fans 14 and 15 are constructed and driven in such a manner that the fans will suck air located above the same in downward direction through the conveyor belt portion and the web arranged thereon immediately above the air fans, and the air leaving the air fans is guided in downward direction by conical air guide means 16 and then laterally deflected by wall portions 16' within the housing to pass in upward direction through the belt portion and the material superimposed thereon which is adjacent to the first-mentioned portion. In the sections 20 and 21 the drying air passes through the web of material 2 from above, while in the sections 22 and 23 the drying air is directed through the web from below. In the sections 20 and 21 the material to be dried is subjected to suction by the action of the fans 14 and 15 and thus is held by suction onto the conveyor belt 7, while in the twosections 22 and 23', which represent pressure zones, the web of material is lifted from the conveyor 7. The direction of air flow is indicated by the arrows 242 9. As can be seen from FIG. 1, the sections 22 and 23 are longer than the sections 20 and 21 and therefore the air passes with a lower speed through the sections 22 and 23 than through the sections 20 and 21.

The apparatus according to the present invention is also provided with means for limiting movement of the web in upward direction away from the conveyor means in the pressure zones 22 and 23. These means may be constituted, as shown in the embodiment illustrated in FIGS. 1-4 by rollers '30 arranged in the sections 22 and 23 at varying distances above the conveyor belt along an upwardly arced curve, the distances 30a, 30b and 300 of these rollers from another increase, as can be seen in FIG. 4, in the direction of travel of the web.

In the sections 22 and 23, heaters 32 and 33 are provided, in the manner known per se, to heat up the drying air and at the same time to assure uniformity of the air flow. These heaters may be constituted by a plurality of tubes through which a heating medium, for instance steam, is passed. Air discharge passages 31 may be provided in the upper wall of the housing 1 to discharge moistened air therefrom and the passage of air through these air passages may be regulated by a fiap adjustably arranged therein.

As shown in FIG. 3, screening plates 36 are arranged to opposite sides of the upper run of the conveyor belt to screen the opposite sides thereof and to guide goods located on the conveyor belt in longitudinal direction.

The above-described drying apparatus will operate as follows:

The web of material introduced from the left side, as viewed in FIG. 1, into the drying chamber is held on the belt by suction in the first section 20 in which warmed-up air will pass in downward direction through the web and evaporation of the surface moisture of the web will take place. In this section the air speed is high. In the following section 22, the web of material is lifted off the conveyor belt by the upwardly directed air flow and forms, in the area of the rollers 30, a series of upwardly arched loops, as shown in FIG. 4. In this section, which is longer than the section 21, the air speed passing through web is lower than the first section and in this section of the dryer a relaxation takes place in the web and thereby a natural shinkage of the web material with simultaneous evaporation of the swelling and capillary water is obtained. In many cases it is sufiicient to provide the dryer only with two sections. If, however, due to the type of material the drying process is not completed at the end of the section 22, then, as shown in the embodiment of FIG. 1, a second pair of drying sections 21 and 23 is provided. Evidently other pairs of drying sections could be provided if this should be necessary for completely drying the material. In each case the first of these sections serves to carry out an intensive drying and in the second section a natural shrinkage and simultaneous further drying will take place.

As shown in FIG. 5, the rollers in the sections 22 and 23 may be designed as stationary hollow rollers 37, provided over an arc which faces the web 38 with holes for the passage of compressed air to flow in the opposite di-v rection to the air flow from the fans, whereby the web of material will contact the roller 37 only with a slight pressure. If the counter air flow provided by the roller 37 is sufficiently high, the material will not come into contact with the roller 37. Compressed air is fed into each of the hollow rollers 37 at one end of the same from a source not shown in the drawing.

As shown in FIG. 6, the rollers arranged in the sections 22 and 23 may be in form of rollers 41 mounted for rotation about their axes and driven, for instance, by sprocket wheels 38 fixed to the ends thereof from a chain 42. The rollers are driven in the direction of the arrow 40. In this case the web 2 abuts against the rollers 41, but due to the rotary motion of the latter and the movement of the material in longitudinal direction, the lines of contact between rollers and webs will constantly change.

FIG. 7 shows another advantageous embodiment of a dryer according to the present invention which corresponds in its essential construction to the dryer shown in FIG. 1, that is, in this case the dryer is also divided into four sections. Webs 44 of material to be dried, particularly tricot material, are, as explained above, introduced onto an endless conveyor belt 43, which acts as a carrier belt. This conveyor belt is advantageously in the form of an air-permeable woven wire belt. Again, two axial flow fans 45 and 46 are arranged at a distance from each other below the upper run of the conveyor belt 43 and these fans may be constructed and driven as explained above so that the belt section immediately above the fans 45 and 46 are suction zones while the following sections 47 and 48 act as the pressure zones. In the arrangement as shown in FIGS. 7 and 8, the means for limiting movement of the web 44 away from the conveyor belt 43 in the pressure zones are constituted by a second conveyor belt 49 having a lower run substantially parallel and upwardly spaced from the upper run of the conveyor belt 43. The second conveyor belt 49 is preferably likewise in the form of flexible air-permeable wire fabric, and the conveyor 49 is supported and guided on rollers 50 and 51. One of the rollers, for instance the roller 51, may be driven, for instance by means of a chain drive from a motor 52, independent from the motor 12 which drives over a chain drive the belt 43. The feed roller which feeds the web- 44 onto the conveyor belt 43 may be likewise driven, for instance 6 by a chain drive from a third motor 53. Each of the motors may be provided with speed-regulating means of known type to regulate the speed of the three motors independently of each other or the transmission between the respective motor and roller may be in the form of a known steplessly variable speed transmission.

The lower run of the upper belt 49 is upwardly spaced from the upper run of the conveyor 43 at a distance which is a multiple of the thickness of the web, and the spacing of the two runs is preferably about 3 to 5 times the web thickness. The air flow, produced by the fans and the air guide means, corresponds substantially to that shown in FIG. 1, as indicated by the arrows drawn in FIGS. 7 and 8. Consequently the web material is lifted in the pressure zones 47 and 48 from the upper run of the lower belt. In this case, however, the web is lifted up to the lower run of the upper conveyor belt 49. Since the adjacent runs of the two belt conveyors are moved in the same direction, the web material is transported in the same direction, whereby the web is loosened and an intensive uniform drying of the same is obtained. The construction shown in FIGS. 7 and 8 has the further advantage that the web of material need not be a continuous coherent layer. For example, individual pieces of elongated material such as tricot underwear need not be connected together, that is, each piece may pass separately through the dryer, because the upper conveyor belt 49 controls, as does the belt 43, the direction of movement and disposition of the pieces of material.

The lower run of the upper conveyor 49 may be supported in the area between the two rollers 50 and 51 by additional support rollers. It is also possible, particularly in very long dryers, to divide the upper conveyor belt into several longitudinal sections, using suit able intermediate return rollers and these sections may be driven by a common drive, for instance by a chain drive. One of the return rollers may be displaceably mounted so as to act as tension roller or additional tensioning rollers may be provided. It is to be understood that the embodiment shown in FIGS. 7 and 8 includes also heating means for heating the air circulated through the conveyor belts and the material interposed therebetween, but for simplification reasons such heating means are not shown in FIG. 7, but they may be arranged, for instance, in the zones 47 and 48.

Evidently, in the embodiment shown in FIGS. 7 and 8, it is also possible to arrange the blowers 45 and 46 in such a manner that the air flow is reversed and the web as it enters into the drying chamber is first moved in engagement with the lower run of the upper belt and subsequently thereto in engagement with the upper run of the lower belt adjacent thereto.

Furthermore, with the arrangement shown in FIGS. 7 and 8, in which the conveyor 43, the conveyor 49 and the feed roller 5 are each separately driven with speeds which can be adjusted individually, it is possible to drive the two conveyors with the same speed as the speed at which the web is fed by the feed roller 5, or to drive each of the conveyors with a speed diiferent from the speed at which the web is fed by the roller 5. The results obtained by driving the two conveyors 43 and 49 and the feed roller 5 with different or the same speeds are illustrated in the schematic FIGS. 9-12. In these figures, the flow of air is, as indicated by the arrows, reversed from the air flow indicated in FIG. 7.

In FIGS. 912, the speed in which the upper run of the lower conveyor belt 43 is moved in longitudinal direction towards the right, as viewed in these figures, is designated by 1/ the speed with which the lower run of the upper conveyor belt 49 is moved in the same direction is indicated by v and the speed with which the web- '44 is fed by the roller 5 into the space between the two runs of the conveyor belts is indicated by 1 Assuming that v is equal to v and that this speed is 6 m./min., whereas the speed v is held at 6.4 m./min.,

that is, that the web 44 is fed with a speed into the space between the conveyor belts which is 0.4 m./min. greater than the speed of the adjacent runs of the conveyor belts 43 and 49, then the web will form folds as indicated in FIG. 9, while abutting alternately against opposite runs of the belts 43 and 49.

FIG. 10 illustrates schematically the configuration the web 44 will take during its passage between the belts 43 and 49 if the speed of the belt 43 is held at 6 m./min., the speed of the belt '49 at m./min., and the initial feed speed of the web 44 at 6.4 m./ min. In other words, in this arrangement, the upper belt 49 moves 1 m./min. slower than the lower belt 43, whereas the speed at which the web 44 is fed into the space between the two conveyor belts is 0.4 m./min. faster than the speed of the lower belt. In this case the web 44 will form folds while abutting against the opposite runs of the two conveyor belts, but these folds are stretched in the portion of the web 44 abutting against the web 43.

FIG. 11 illustrates the configuration the web 44 will take between the opposite runs of the belts when the speed V of the lower conveyor belt is held at 6 m./min., the speed v of the upper conveyor belt is held at 7 m./min. and the speed 1 at which the web 44 is fed into the space between the belts is 6.4 m./ min. In this case in which the upper conveyor belt runs faster and the lower conveyor belt slower than the speed at which the web 44 is fed between the belts, the web will be stretched while abutting against the upper belt and form folds while abutting against the lower belt.

Finally, FIG. 12 illustrates the configuration the web 44 will take when the speeds of the upper and lower belts are equal to the speed at which the web 44 is fed between the belts. In this case, evidently, the web 44 will not form any folds while respectively abutting against the lower run of the upper belt or the upper run of the lower belt.

By varying the speeds at which the two belts are driven and at which the web is fed into the space between the belts, it is therefore possible to additionally relax the tension in the web while the same is alternately moved into engagement with the opposite runs of the two belts.

It will be understood that each of the elements dedescribed above, or two or more together, may also find a useful application in other types of apparatus for continuousl drying web material diflering from the types describe above.

While the invention has been illustrated and described as embodied in apparatus for continuously drying web material, especially textile material, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from. the spirit of the present invention.

Thus, while the drawings show the conveyor means eXtending in substantially horizontal direction, it is evidently also possible to use the principle according to the present invention in apparatus in which the conveyor means are arranged inclined to the horizontal direction or even vertically so that gravity will support transporting of the web. Such an inclined or vertical arrangement of the conveyor means will also advantageously reduce the floor-space requirements of the apparatus.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. Apparatus for continuously drying air permeable web material, comprising, in combination, elongated airpermeable conveyor means for transporting a web to be dried in longitudinal direction; means for sucking air at at least one longitudinal portion of the conveyor means in a first direction through said conveyor means and the web superimposed thereon so that the web will be held in engagement with said conveyor means and for blowing air at at least another longitudinal portion of said conveyor means adjacent to said one portion in a direction opposite to the first direction through said conveyor means so as to lift the web from said other portion of said conveyor means; and means arranged at least along said other portion of said conveyor means spaced in said opposite direction therefrom for limiting movement of the web away from said conveyor means.

2. An apparatus as defined in claim 1, wherein said other longitudinal portion of the conveyor means follows said one portion in direction of movement of said conveyor means.

3. An apparatus as defined in claim 1, and including heating means for heating the air passing through said conveyor means and the web.

4. An apparatus as defined in claim 3, and including an elongated housing having an inlet end and an outlet end, said conveyor means passing through said inlet end into said housing and leaving the latter through said outlet end, said heating means being located in said housing so that the latter forms a heating chamber, and means for superimposing a web to be dried onto said conveyor means in the region of said inlet end of said housing.

5. An apparatus as defined in claim 4, wherein said means for sucking air in said first direction through said one portion of said conveyor means and for blowing air in said second direction through said other portion of said conveyor means comprises fan means arranged in said housing and having an air discharge end and means for deflecting the air leaving the air discharge end to pass in said second direction through said other portion of the conveyor means.

6. An apparatus as defined in claim 5, wherein said heating means are arranged for heating the deflected air before it passes through said other portion of said conveyor means.

7. An apparatus as defined in claim 1, wherein said means for limiting movement of said web away from said other portion of said conveyor means comprises a plurality of rollers extending spaced from each other in direction of movement of said conveyor means and transverse to said direction and spaced in said second direction from said other portion of said conveyor means.

8. An apparatus as defined in claim 7, and including means mounting said rollers turnable about their axes and drive means connected to said rollers for rotating the same about their axes.

9. An apparatus as defined in claim 8, and including means cooperating with said drive means of said rollers for adjusting the rotational speed of the latter independent from the speed of said conveyor means.

10. An apparatus as defined in claim 8, wherein said drive means for said rollers comprises a chain drive.

11. An apparatus as defined in claim 7, wherein said rollers are hollow and provided on the side thereof facing said conveyor means and said web thereon with a plurality of openings directed towards said web, and including means stationarily mounting said rollers and means for feeding air under pressure into the hollow rollers so that the air will pass through said openings towards said web.

12. An apparatus as defined in claim 7, wherein the axes of said rollers are arranged along a line curving away from said other portion of said conveyor means.

13. An apparatus as defined in claim 12, wherein the distance between adjacent rollers increases in direction of movement of said web.

14. An apparatus as defined in claim 1, wherein said means for limiting movement of the Web away from said second portion of said conveyor means comprises a second elongated air-permeable conveyor means extending substantially parallel and spaced in said opposite direction from said first-mentioned conveyor means at least along said other portion of the latter and moving in the same direction.

15. An apparatus as defined in claim 14, wherein the distance between adjacent runs of said first and said second conveyor means is a multiple of the thickness of the web to be dried.

16. An apparatus as defined in claim 14, wherein said first and said second conveyor means each comprise an endless flexible air-permeable wire mesh.

17. An apparatus as defined in claim 14, and including an elongated housing having an inlet end and an outlet end, said first conveyor means comprising an endless band having a run passing through said inlet end into said housing and leaving the latter through said outlet end and first drive means for moving said band at a predetermined speed, said second conveyor meanscomprising a second endless band in said housing and having a run extending substantially parallel and spaced from said run of said first conveyor means and second drive means for driving said second conveyor means, rotatable means for continuously feeding a web to be dried onto one of said References Cited UNITED STATES PATENTS 2,225,505 12/1940 Ofien 34-160 3,230,634 1/1966 Sachs 34--156 X 3,359,648 12/1967 Overly et al 34-162 X 3,377,056 4/1968 Boye 34-160 KENNETH W. SPRAGUE, Primary Examiner US. Cl. X.R. 34-160 

